Hydraulic Radius of a Pipe

Hydraulic radius, abbreviated as \(r_h\), also called hydraulic mean radius, is a measure of the area cross-section available for flow in an open channel or pipe.  It is used in fluid mechanics and in calculations related to fluid flow, such as in the Manning's equation for open channel flow or the Darcy-Weisbach equation for pipe flow. 

 

 

 

 

 

 

Hydraulic radius of a Pipe formula
\( r_h =   A_c \;/\; P_w \)  \( A_c =  r_h \; P_w \)  \( P_w =  A_c \;/\; r_h \)
Symbol	English	Metric
\( r_h \) = hydraulic radius	\( in \)	\(mm\)
\( A_c \) = area cross-section of flow	\( in^2 \)	\( mm^2 \)
\( P_w \) = wetting perimeter	\( in \)	\( mm \)